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evaluate inherit (from) exprs only once per directive

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desugaring inherit-from to syntactic duplication of the source expr also
duplicates side effects of the source expr (such as trace calls) and
expensive computations (such as derivationStrict).
This commit is contained in:
pennae 2024-01-27 16:33:34 +01:00
parent ecf8b12d60
commit cefd0302b5
9 changed files with 109 additions and 15 deletions
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24
src/libexpr/eval.cc
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@ -1186,6 +1186,18 @@ void ExprPath::eval(EvalState & state, Env & env, Value & v)
}
Env * ExprAttrs::buildInheritFromEnv(EvalState & state, Env & up)
{
Env & inheritEnv = state.allocEnv(inheritFromExprs->size());
inheritEnv.up = &up;
Displacement displ = 0;
for (auto from : *inheritFromExprs)
inheritEnv.values[displ++] = from->maybeThunk(state, up);
return &inheritEnv;
}
void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
{
v.mkAttrs(state.buildBindings(attrs.size() + dynamicAttrs.size()).finish());
@ -1197,6 +1209,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
Env & env2(state.allocEnv(attrs.size()));
env2.up = &env;
dynamicEnv = &env2;
Env * inheritEnv = inheritFromExprs ? buildInheritFromEnv(state, env2) : nullptr;
AttrDefs::iterator overrides = attrs.find(state.sOverrides);
bool hasOverrides = overrides != attrs.end();
@ -1209,9 +1222,9 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
Value * vAttr;
if (hasOverrides && !i.second.inherited()) {
vAttr = state.allocValue();
mkThunk(*vAttr, *i.second.chooseByKind(&env2, &env, &env2), i.second.e);
mkThunk(*vAttr, *i.second.chooseByKind(&env2, &env, inheritEnv), i.second.e);
} else
vAttr = i.second.e->maybeThunk(state, *i.second.chooseByKind(&env2, &env, &env2));
vAttr = i.second.e->maybeThunk(state, *i.second.chooseByKind(&env2, &env, inheritEnv));
env2.values[displ++] = vAttr;
v.attrs->push_back(Attr(i.first, vAttr, i.second.pos));
}
@ -1244,10 +1257,11 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
}
else {
Env * inheritEnv = inheritFromExprs ? buildInheritFromEnv(state, env) : nullptr;
for (auto & i : attrs) {
v.attrs->push_back(Attr(
i.first,
i.second.e->maybeThunk(state, *i.second.chooseByKind(&env, &env, &env)),
i.second.e->maybeThunk(state, *i.second.chooseByKind(&env, &env, inheritEnv)),
i.second.pos));
}
}
@ -1282,6 +1296,8 @@ void ExprLet::eval(EvalState & state, Env & env, Value & v)
Env & env2(state.allocEnv(attrs->attrs.size()));
env2.up = &env;
Env * inheritEnv = attrs->inheritFromExprs ? attrs->buildInheritFromEnv(state, env2) : nullptr;
/* The recursive attributes are evaluated in the new environment,
while the inherited attributes are evaluated in the original
environment. */
@ -1289,7 +1305,7 @@ void ExprLet::eval(EvalState & state, Env & env, Value & v)
for (auto & i : attrs->attrs) {
env2.values[displ++] = i.second.e->maybeThunk(
state,
*i.second.chooseByKind(&env2, &env, &env2));
*i.second.chooseByKind(&env2, &env, inheritEnv));
}
auto dts = state.debugRepl